Automatic choke mechanism



g- 2, 1966 P. E. BRAUN ETAL 3,263,972

AUTOMATIC CHOKE MECHANISM Filed June 20, 1963 4 Sheets-Sheet 1 PAUL E.BRA UN ALBERT APRUCHIVO ATTORNEYS 1966 P. E. BRAUN ETAL 3,

AUTOMATIC CHOKE umcmmxsm Filed June 20, 1963 4 Sheets-Sheet 2 PAUL E.BRAUN A L BERT A. PRUCH/VO INVENTO ATTORNEYS Aug. 2, I966 P. E. BRAUNETAL 3,263,972

AUTOMATIC CHOKE MECHANISM Filed June 20, 1963 4 Sheets-Sheet 5 FIG. 6

PAUL E. BRAUN A 1. BERT A. mum/v0 INVENTORS ATTORNEYS Aug. 2, 1966 P. E.BRAUN ETAL AUTOMATIC CHOKE MECHANISM 4 Sheets-Sheet 4 Filed June 20,I963 PA UL E. BRAU/V ALBERT AEBQUCHNO INVE ATTORNEYS United StatesPatent 3,263,972 AUTOMATIC CHOKE MECHANISM Paul E. Braun, Birmingham,and Albert A. Pruchno, Detroit, Mich., assignors to Ford Motor Company,Dearborn, Mich., a corporation of Delaware Filed June 20, 1963, Ser. No.289,258 6 Claims. (Cl. 261-39) This invention relates to an automaticchoke mechanism for an internal combustion engine carburetor and moreparticularly to an adjustable linkage for an automatic choke mechanism.

The thermally responsive element of a conventional automatic chokemechanism positions both a choke valve and a fast idle mechanism. Thefast idle mechanism increases the engine idle speed during the initialstage of warm up to prevent stalling. It is desirable to provide foradjustment of the choke valve and fast idle mechanism relative to thethermally responsive element to compensate for production variations anddiffering engine requirements. Adjustment of the choke valve isparticularlyrequired when the choke mechanism employs a suction motor topartially open the choke valve when a cold engine first commences torun. The adjustment is necessary to calibrate the degree of choke valveopening or pull down effected by the suction motor.

Automatic choke mechanisms previously known frequently have notpermitted the fast idle mechanism and the degree of choke valve pulldown to be independently adjusted. In addition it was often necessary topermanently deform a portion or portions of the choke linkage to producethe desired adjustments. Deformation of the linkage could only beaccomplished through the use of special tools and did not permit theexacting degree of adjustment required.

It is therefore the principal object of this invention to provide anautomatic choke mechanism in which independent adjustment of the chokevalve and fast idle mechanism with respect to the thermally responsiveelement is possible.

It is a further object of this invention to provide a simplified chokelinkage adjustment mechanism that permits delicate adjustments to bemade.

A carburetor embodying this invention comprises an induction passagecontaining throttle and choke valves. A temperature responsive elementis connected to the choke valve by an adjustable length link to actuatethe choke valve in response to temperature variations. A lever rotatablewith the throttle valve is adapted 'to engage a fast idle cam toestablish a fast idle position for the throttle valve. The fast idle camis adjustably connected to the temperature responsive element.

Further objects and advantages of this invention will become moreapparent when considered in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a side elevational view of an internal combustion enginecarburetor incorporating this invention.

FIGURE 2 is a front elevational view of the carburetor shown in FIGURE1;

FIGURE 3 is an exploded view showing the automatic choke mechanismincorporated in the carburetor.

FIGURES 47 are partially exploded side elevational views of the chokemechanism, with portions shown in cross section, illustrating thesequence of operation.

FIGURE 4 shows the mechanism during cranking of a cold engine.

FIGURE 5 shows the position of the mechanism immediately after theengine has started.

FIGURE 6 shows the choke mechanism as it appears when the engineapproaches its operating temperature.

FIGURE 7 illustrates a position the mechanism may take to permit manualopening of the choke valve to start a flooded engine.

FIGURE 8 is a cross sectional view taken along line 8-8 of FIGURE 1.

FIGURE 9 is a cross sectional view in part similar to FIGURE 8 showingthe elements prior to fina'l adjustment.

Referring now in detail to the drawings, a carburetor is indicatedgenerally by the reference numeral 11. Formed within the carburetor 11is at least one induction passage 12. A throttle valve 13 is rotatablysupported in the induction passage 12 upon a throttle valve shaft 14.The throttle valve shaft 14 extends from each side of the carburetor 11and one side is connected through throttle linkage 15 to an acceleratormechanism to permit adjustment of the speed of the associated engine(not shown). An inturned tang 16 of the throttle linkage 15 contacts anadjustable screw 17 to establish a normal engine idle speed.

Positioned in the induction passage 12 anterior to the throttle valve 13is a choke valve 18. The choke valve 18 is rota-tably supported upon achoke valve shaft 19 that extends outwardly at one side of thecarburetor 11. The choke valve 18 is rotatably positioned in theinduction passage 12 in response to temperature variations by anautomatic choke mechanism indicated generally at 21.

The automatic choke mechanism 21 includes a choke housing 22 having aplurality of inwardly extending, apertured bosses 23. Outward-1yextending bosses 24 formed upon the carburetor 11 are tapped to receivebolts 25 that extend through the apertured bosses 23 to secure the chokehousing 22 to the carburetor 11. A cover plate 26 encloses the chokehousing 22 and is secured thereto by a plurality of bolts 27 that passthrough elongated apertures 28 in the choke housing cover 25. The bolts27 are threaded into tapped holes 29 formed around the periphery of thechoke housing 22.

A coiled thermally responsive spring 31 is contained within the coverplate 26 and has its inner end 32 affixed thereto. The thermallyresponsive spring 31 is insulated from the interior of the choke housing22 by a composition disc 33 and steel disc 34 that are interposedbetween the cover plate 26 and the choke housing 22.

The outer end 35 of the thermally responsive spring 31 is aifixed to abifurcated arm 36 of a choke actuating lever 37. The choke actuatinglever 37 is aflixed by a screw 39 to a choke actuating shaft 38 that isjournaled in the choke housing 22. The bifurcated arm 36 extends througharcuate slots 40 and 41 formed in the composition and steel discs 33 and34, respectively.

The choke actuating shaft 38 extends inwardfy toward the carburetor 11and has a lever 42 affixed to its inner end. A link 43 has an outturnedend 44 that extends through an aperture in the lever 42. The outturnedend 44 of the link 43 is retained in the aperture by -a snap ring 45 topermit the transmission of motion from the lever 42 to the link 43. Theupper end of the link 43 is pivotally connected to a lever 46 that isaflixed for rotation with the choke shaft 19 by an adjustable swivelmechanism indicated generally at 47.

The adjustable swivel mechanism 47, which is shown in greater detail inFIGURES 8 and 9, permits the relative positions of the choke valve 18and choke actuating shaft 38 to be adjusted. The adjustable swivelmechanism 47 includes a first generally cylindrical shaped element 48having an inwardly extending boss 49. A headed rivet 51 extends throughan aperture formed in the lever 46 and is fixed in an aperture 52 formedin the inwardly extending boss 49. The rivet 51 pivotally connects thelever 46 to the element 48.

A second element 53 of the adjustable swivel mechanism 47 has acylindrical portion 54 that extends through and is journaled in theinternal bore of the first element 48. The second element 53 is axiallyfixed with respect to the first element 48 by the contact of a shoulder55 with the upper surface of the eement 48 and the contact of anoverturned flange 56 with the lower surface of the element 48. Thesecond element 53 is internally threaded, as at 57, to cooperate withthreads 58 formed on the upper end of the link 43.

The relative positions of the choke valve 18 and choke act ating shaft38 may be adjusted by rotating the internally threaded element 53.Rotation of the element 53 causes the adjustable swivel mechanism 47 tomove axially along the link 43 to adjust the effective length of thelink 43. Once the desired relative positions of the choke valve 18 andchoke actuating shaft 38 are obtained, the adjustable swivel 47 may berigidly fixed upon the link 43. For this purpose, a groove 59 is formedaround the periphery of the element 43 adjacent its internal threads 57.By engaging a tool with the groove 59 and compressing the element 53,the threads 57 are deformed (FIGURE 8) to fix the adjustable swivelmechanism 47 in position. By staking the adjustable swivel mechanism 47to the link 43, play is eliminated from the choke actuating linkage. Theadjustment of the effective length of the link 43 also determines thedegree of the vacuum pull down of the choke valve 18 effected by thesuction motor now to be described.

The choke housing 22 is formed with a cylindrical bore 61 that slidablyreceives a vacuum actuated piston 62. The piston 62 is pivotallyconnected by a pin 63 to a link 64. The piston 62 is transverselyslotted, as at 65, to provide clearance for the link 64. The upper endof the link 64 is pivotally connected by a pin 66 to an extending arm 67of the choke actuating lever 37.

The cylindrical bore 61 is exposed to engine intake manifold vacuum bymeans of a port 68 that opens into one of the longitudinal grooves 69formed at each side of the bore 61. The port 68 extends through one ofthe choke housing bosses 23 and carburetor bosses 24 to a point in theinduction passage 12 below the throttle valve 13. The lower end of thecylindrical bore 61 is closed by a disc 71. The intake manifold vacuumacting on the head of the piston 62 modulates the position of the chokevalve 18 in the manner which will be described as this descriptionproceeds.

The thermally responsive spring 31 is also adapted to provide anincreased engine idle speed during the initial stage of engine warm upby means of the fast idle mechanism indicated generally at 72. The fastidle mechanism 72 comprises a lever 73 that is rotatably journaled onthe choke actuating shaft 38 between the lever 42 and the choke housing22. A link 74 transmits motion between the lever 73 and a fast idle cam75 that is pivotally journaled upon the carburetor 11 by a pin 76. Thelink 74 is fixed relative to the lever 73 and the fast idle cam 75 bysnap rings 77 and 78, respectively. The lever 73 has an inturned tang 79through which is threaded an adjustable screw 81. The adjustable screw81 is adapted to abut at times an upper surface 82 of the lever 42. Alever 83 is aflixed to the outwardly extending side of the throttlevalve shaft 14 adjacent the automatic choke mechanism 21 by a nut 84. Anadjustable screw 85 is threaded through the lever 83 and is adapted toengage the stepped cam surface 86 formed on the fast idle cam 75.Adjustment of the screw 81 permits variation in the position of the fastidle cam 75 with respect to the choke actuating shaft 38.

Operation When the engine has been standing for a long duration underlow ambient temperatures, the automatic choke mechanism 21 is permittedto appropriately position the choke valve 18 by opening the throttlevalve 13. Opening of the throttle valve 13 permits the linkage to movefree of interf ren e rom the fast idle mechanism 72. If the temperatureis sufficiently low, the thermally responsive spring 31 will rotate thechoke actuating lever 37 and choke actuating shaft 38 in acounterclockwise direction an amount sufficient to fully close the chokevalve 18 (FIGURE 4). The contact of the upper surface 82 of lever 42with the adjustable screw 81 also causes the lever 73 to be rotated in acounterclockwise direction. This motion is transmitted through the link74 to the fast idle cam 75. When the throttle valve 13 is closed, theadjustable screw 85 will contact the high portion of the cam surface 86on the fast idle cam 75 to cause the throttle valve 13 to be held in amore fully opened position than the normal idle speed.

The linkage remains in the position shown in FIGURE 4 during cranking ofthe cold engine. During this time the intake manifold vacuum exertedthrough the port 68 below the piston 62 is insufficient to have anyeffect on the position of the choke actuating shaft 38. When the enginecommences to run, however, the intake manifold vacuum increasessignificantly. The increase in vacuum exerted in the cylindrical bore 61causes the piston 62 to be drawn downwardly and rotate the chokeactuating lever 37 in a clockwise direction (FIGURE 5). This motionopens the choke valve 18 slightly to permit suflicient air flow throughthe induction passage 12 for sustained engine operation. The opening ofthe choke valve 18 may also be assisted by unbalancing the choke valve18 upon choke valve shaft 19.

The degree of movement of the piston 62 is limited by registry of thetransverse slot in the piston 62 with the longitudinal grooves 69 formedin the cylinder 61. When this happens, a vacuum bleed will occur pastthe piston 62 and further downward movement of the piston can only occurupon a significant increase in manifold vacuum.

The vacuum bleed occurring past the piston 62 is utilized to draw heatedair into the choke housing 22 for heating the thermally responsivespring 31 in response to engine operation. Air heated by an exhaustmanifold stove (not shown) is drawn through an inlet tube 87 formedintegrally with the choke housing 22. The inlet tube is ported through aconduit 88 into the choke housing. The conduit 88 registers withapertures 89 and 91 formed in the steel and composition discs 34 and 33,respectively. The heated air is drawn from the exhaust stove through theinlet tube 87 and conduit 88 into the choke housing cover 26. The heatedair passes across a thermally responsive spring 31 and passes throughthe slotted apertures 39 and 41 into the choke housing 22. From thechoke housing 22 the heated air bypasses the piston 62 and is dischargedinto the induction system of the engine through the port 68.

As the thermally responsive spring 31 is heated in response to engineoperation, its tension decreases and the choke actuating lever 37 andchoke actuating shaft 38 are rotated in a clockwise direction. Theclockwise rotation of the choke actuating shaft 37 is transmittedthrough the lever 42 and link 43 to the choke valve 18 (FIGURE 6).

The lever 73, link 74 and fast idle cam are unbalanced so that gravitytends to rotate the fast idle cam 75 in a clockwise direction. Theclockwise rotation is limited by the contact of the adjustable screw 81with the upper surface 82 of the lever 42. A fast idle speed is notrequired after the initial stage of engine warm up and, accordingly, thefast idle cam 75 is permitted to rotate free from contact with theadjustable screw 85. The rotation of the fast idle cam 75 is limited bycontact of the fast idle cam 75 with an inwardly extending boss 92formed on the choke housing 22. The choke actuating mechanism maycontinue to rotate, however. Continued opening of the choke valve 18causes the lever 42 to move away from the adjustable screw 81 (FIGURE6).

If the engine is stopped, the thermally responsive element will cool andcause the choke valve 18 to rotate toward a closed position. Continuedrotation will eventually cause the lever 42 to again contact theadjustable screw 81 and actuate the fast idle cam 75. The time ofactuation may be varied by adjustment of the screw 81.

It is possible that, due to improper starting procedure, the cold enginemay be flooded. Provision is mad-e, therefore, for manual opening of theotherwise closed choke valve 18 to permit unflooding and starting of theengine. For this purpose, the lever 83 is formed with an outwardlyextending tang 93. By rotating the throttle valve 13 into a fully openedposition (FIGURE 7), the tang 93 is brought into abutment with the fastidle cam 75. The contact causes the fast idle cam 75 to be rotated in aclockwise direction and this motion is transmitted through the link 74to the lever 73. The clockwise rotation of the lever 73 is transmittedthrough the adjustable screw 81 to clockwise rotation of the lever 42 toopen the choke valve 18 slightly and permit starting.

It is to be understood that various changes and modifications may bemade from the described, preferred embodiment of the invention withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

We claim:

1. A carburetor for an internal combustion engine comprising aninduction passage, a throttle valve and a choke valve rotatablysupported in said induction passage, a temperature responsive element,an adjustable length link operably connecting said temperatureresponsive element to said choke valve for moving said choke valvebetween an opened and a closed position in response to temperaturechanges, a lever rotatable with said throttle valve, a fast idle camadapted to be engaged by said lever to establish a fast idle positionfor said throttle valve, and an operative connection between saidtemperature responsive element and said fast idle cam for positioningsaid fast idle cam to be engaged by said lever at low temperatures, saidlast named operative connection comprising an adjustable abutment screwto permit adjustment of the relative positions of said temperatureresponsive element and said fast idle cam independent of adjustment ofthe relative positions of said temperature responsive element and saidchoke valve.

2. A carburetor for an internal combustion engine comprising aninduction passage, a throttle valve rotatably supported in saidinduction passage, a choke valve rotatably supported in said inductionpassage anterior to said throttle valve, a temperature responsiveelement, a first lever connected to said temperature responsive elementfor movement in response to temperature variations, an adjustable lengthlink operatively connecting said first lever to said choke valve, asecond lever having an adjustable lost motion connection with said link,said lost motion connection being adjustable independently of saidadjustable length link, said connection including adjustable screwmeans, a fast idle cam positioned by said second lever, and a thirdlever operatively connected to said throttle valve, said third leverbeing adapted to engage said fast idle cam at low temperatures toestablish a fast idle position for said throttle valve.

3. A carburetor for an internal combustion engine comprising aninduction passage, a throttle valve, a choke valve rotatably supportedin said induction passage upon a choke valve shaft, a temperatureresponsive element, a first lever operatively connected to saidtemperature responsive element for movement in response to temperaturevariations, a second lever fixed for rotation with said choke valveshaft, a link having pivotal connections with said levers fortransmitting motion between said temperature responsive element and saidchoke valve, at least one of said pivotal connections comprising a firstelement pivotally connected to the lever and a second element rotatablewith respect to said first element, said first and second elements beingconnected for simultaneous axial movement, said second element having athreaded connection with said link for adjustment of the axial positionof said elements upon said link, a third lever in adjustable abutmentwith said first lever, and a fast idle cam positioned by said thirdlever, said cam positioning said throttle valve to establish a fast idleposition.

4. A carburetor as defined by claim 3 wherein said second element ispermanently deformable to permit it to be locked in its adjustedposition upon the link.

5. A carburetor for an internal combustion engine comprising aninduction passage, a throttle valve rotatably supported upon a throttlevalve shaft in said induction passage, a choke valve rotatably supportedupon a choke valve shaft in said induction passage anterior to saidthrottle valve, a temperature responsive element, a first leverrotatably positioned by said temperature responsive element in responseto temperature variations, a second lever fixed for rotation with saidchoke valve shaft, a link pivotally connected to said first and secondlevers for positioning said choke valve in response to temperaturevariations, a fast idle cam pivoted with respect to said carburetor, athird lever pivoted with respect to said carburetor and having anadjustable abutment adapted to contact said first lever, a second linkpivotally connected to said fast idle cam and said third lever, saidfast idle cam, said second link and said third lever being unbalancedfor pivotal movement to bring said adjustable abutment into engagementwith said first lever when the choke valve is in a closed position, anda fourth lever fixed for rotation with said throttle valve shaft andhaving an adjustable abutment adapted to engage said fast idle cam toestablish a fast idle position for said throttle valve under low ambienttemperatures.

6. A carburetor as defined by claim 5 wherein one of the pivotalconnections between said first link and said first and second levers isadjustable to change the relationship between said first lever and saidchoke valve.

References Cited by the Examiner UNITED STATES PATENTS 2,124,778 7/1938Hunt 261-52 X 2,136,353 11/1938 Weber 26152 2,555,124 5/1951 Gothberg74586 X 2,747,848 5/1956 Kehoe 26152 3,151,189 9/1964 McSeveny 261-39HARRY B. THORNTON, Primary Examiner.

ROBERT F. BURNETT, Examiner.

T. R. MILES, Assistant Examiner.

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING ANINDUCTION PASSAGE, A THROTTLE VALVE AND A CHOKE VALVE ROTATABLYSUPPORTED IN SAID INDUCTION PASSAGE, A TEMPERATURE RESPONSIVE ELEMENT,AN ADJUSTABLE LENGTH LINK OPERABLY CONNECTING SAID TEMPERATURERESPONSIVE ELEMENT TO SAID CHOKE VALVE FOR MOVING SAID CHOKE VALVEBETWEEN AN OPENED AND A CLOSED POSITION IN RESPONSE TO TEMPERATURECHANGES, A LEVER ROTATABLE WITH SAID THROTTLE VALVE, A FAST IDLE CAMADAPTED TO BE ENGAGED BY SAID LEVER TO ESTABLISH A FAST IDLE POSITIONFOR SAID THROTTLE VALVE, AND AN OPERATIVE CONNECTION BETWEEN SAIDTEMPERATURE RESPONSIVE ELEMENT AND SAID FAST IDLE CAM FOR POSITIONINGSAID FAST IDLE CAM TO BE ENGAGED BY SAID LEVER AT LOWER TEMPERATURES,SAID LAST NAMED OPERATIVE CONNECTION COMPRISING AN ADJUSTABLE ABUTMENTSCREW TO PERMIT ADJUSTMENT OF THE RELATIVE POSITIONS OF SAID TEMPERATURERESPONSIVE ELEMENT AND SAID FAST IDLE CAM INDEPENDENT OF ADJUSTMENT OFTHE RELATIVE POSITIONS OF SAID TEMPERATURE RESPONSIVE ELEMENT AND SAIDCHOKE VALVE.